Fiducial marker devices, tools, and methods

ABSTRACT

This document discusses, among other things, fiducial marker devices, tools, and methods. One example illustrates a combined imagable fiducial locator and divot for receiving a positioning wand of an image-guided surgical (IGS) workstation. A further example is reflective such that it is locatable by a remote detector of an optical positioning system. A generally cylindrical (e.g., faceted cylindrical) columnar locator permits easy application of reflective tape. Other examples discusses a unitary fiducial marker with multiple divots and a swiveling and/or tilted fiducial marker divot, each of which allows manipulation of a positioning wand into a remote camera&#39;s field of view. Another example includes at least one reflector that can be aimed. A further example discusses an imagable fiducial marker carrier that is attachable to a single location on a patient&#39;s skull to reduce trauma. A keying arrangement fixedly defines the orientation of the carrier, allowing detachment and reattachment in the same orientation.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.10/374,677 filed Feb. 25, 2003. The entire disclosure of the aboveapplication is incorporated herein by reference.

FIELD OF THE INVENTION

This document relates generally to imaging and/or locating a subject,such as for performing surgical intervention, and more specifically, butnot by way of limitation, to fiducial marker devices and associatedtools and methods.

BACKGROUND

Fiducial markers that can be located and recognized by an imaging systemor other system are useful in neurosurgery and other applications.Examples of imaging system modalities include, among other things,magnetic resonance imaging (MRI), computed tomography (CT), positronemission tomography (PET), and single photon emission computedtomography (SPECT).

For example, in one technique, multiple fiducial markers are screwedinto the patient's skull to define landmarks recognizable by an imagingsystem. The imaging system is used to obtain one or more preoperativeimages of the patient's brain. Recognizable images of the fiducialmarkers appear on such preoperative images. Such a bone-anchoredfiducial marker typically includes an externally threaded bone-screwportion, which is driven into the skull. A threaded shaft rises up andout of the skull from the bone-screw. The threaded shaft typicallyreceives a screwed-on imagable sphere that is visible on an MRI or CTimage. The multiple fiducial markers on the patient's skull definelandmarks on preoperative images that are useful to the physician forplanning entry coordinates on the patient's skull and for planning atrajectory to a target location in the brain. An image-guided surgicalworkstation uses these preoperative images and the planning data toguide the neurosurgeon while actually performing the subsequent surgicalprocedure.

After the preoperative planning phase, the patient is brought into theoperating room so that the planned surgical procedure can be performed.On the operating table, the patient's skull is clamped in a head-frameor otherwise immobilized. In order to use the preoperative imagesprovided by the image-guided workstation to guide the surgeon during thesurgical procedure, the patient's skull must first be “registered” tothe preoperative images. The registration creates an association between(1) the actual physical location of the fiducial markers on thepatient's skull in the operating room and (2) the locations of theimages of the fiducial markers visible on the preoperatively-obtainedimages. This allows mapping between the actual space in which thepatient is located to the space defined by the preoperative images.

According to one registration technique, a “wand” is used to performthis patient registration. The wand typically includes multiplelight-emitting diode (LED) locators or reflective locators, which arevisible to an infrared camera or other detector of an opticalpositioning system in the operating room. The camera and opticalpositioning system are operatively connected to the image-guidedworkstation. The locators define the position of the wand in theoperating room, including the position of a sharp tip portion of thewand, which is in a known physical relationship to the locators. Toregister the patient, the imagable spheres are unscrewed from thefiducial marker shafts, and replaced by respective “divots” that aresized and shaped to receive the wand tip. These divots are screwed ontothe respective fiducial marker shafts, such that when the wand tip isreceived into the maximum depression point of the divot, the wand tipthen corresponds to the same location as the center of the imagablesphere when the imagable sphere was screwed onto the fiducial markershaft. A reference divot is typically also present in the operating roomat a known location, such as attached to the operating table or thepatient's skull-immobilizing head-frame. During the patient registrationprocess, the surgeon touches the wand tip to the reference divot (toprovide an absolute positional reference to the image-guidedworkstation), and then to each fiducial marker divot. This permits theimage-guided workstation to correlate the actual physical location ofthe patient's skull to the preoperative images. The physician can thenuse the wand, in conjunction with the preoperative images provided bythe image-guided workstation, to locate an appropriate entry point andtrajectory to the target in the brain.

The present inventors have recognized that problems with the aboveregistration procedure include patient discomfort caused by the presenceof the fiducial markers, increased trauma to the patient resulting fromusing multiple fiducial markers screwed into different locations of thepatient's skull, the difficulty of unscrewing the imaging spheres andreplacing them with the registration divots, a limited field of view ofthe camera used in the operating room, and the difficulty ofconstructing a multi-modal fiducial marker that can be recognized bymore than one imaging modality or positioning system. Moreover, thepresent inventors have recognized the desirability of streamlining theregistration process to reduce its time and cost. For these and otherreasons, which will become apparent upon reading the following detaileddescription and viewing the drawings that form a part thereof, thepresent inventors have recognized an unmet need for improved fiducialmarker devices, tools, and methods.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, which are not necessarily drawn to scale, like numeralsdescribe substantially similar components throughout the several views.Like numerals having different letter suffixes represent differentinstances of substantially similar components. The drawings illustrategenerally, by way of example, but not by way of limitation, variousembodiments discussed in the present document.

FIG. 1A is a schematic diagram illustrating generally one example of animagable fiducial marker that includes a built-in conical divot or othermale or female receptacle, or the like.

FIG. 1B is a schematic diagram illustrating generally one example of animagable fiducial marker that omits the divot illustrated in FIG. 1A,but which is both locatable by a remote positioning system and imagableby one or more imaging modalities.

FIG. 2A is a schematic diagram illustrating generally an alternativeexample of a fiducial marker that includes a cylindrical imagingfiducial locator and a conical or other divot or other receptacle forreceiving a positioning wand tip or the like.

FIG. 2B is a schematic diagram illustrating generally one example of animagable fiducial marker that omits the divot illustrated in FIG. 2A,but which is both locatable by a remote positioning system and imagableby one or more imaging modalities.

FIG. 3A is a schematic diagram illustrating generally one example of apositioning wand for use in conjunction with a remotely-located cameraor other like device of an optical positioning system, such as can becoupled to an image-guided surgical workstation in an operating room.

FIG. 3B is a schematic diagram, similar in certain respects to FIG. 3A,illustrating generally one example of a positioning wand includingenergy reflective surfaces that are capable of being oriented or aimedtoward a remote detector.

FIG. 3C is a perspective view schematic diagram illustrating generally,by way of example, but not by way of limitation, certain generally“cylindrical” columnar structures having faceted lateral peripheralsurfaces.

FIG. 3D is a schematic diagram illustrating generally an example of apositioning wand with flat disk-shaped pieces of reflective tape areattached in a known configuration.

FIG. 4 is a schematic diagram illustrating generally, by way of example,but not by way of limitation, an image guided surgical (IGS) computerworkstation to which an optical positioning system is coupled.

FIG. 5 is a schematic diagram illustrating generally a unitary divotassembly that includes multiple divots.

FIG. 6A is a schematic diagram illustrating generally a divot assemblythat includes a swiveling tilted head carrying a conical or other divotor the like.

FIG. 6B is a schematic diagram illustrating generally a locator assemblythat includes a swiveling tilted head including a surface that reflectselectromagnetic energy.

FIG. 7A is a schematic diagram illustrating generally a divot assemblythat includes a swiveling and pivotable head carrying a conical or otherdivot.

FIG. 7B is a schematic diagram illustrating generally a divot assemblythat includes a swiveling and pivotable head including a surface thatreflects electromagnetic energy.

FIG. 8 is a schematic diagram illustrating conceptually a fiducialmarker carrier that is attachable to (and also detachable from) a singlelocation on the patient's skull, thereby reducing trauma to the patient.

FIG. 9 is an exploded view schematic diagram illustrating generally oneexample of the carrier, including a frame, a post, and a base.

FIG. 10 is a schematic diagram illustrating a portion of a fiducialmarker carrier that includes at least one antirotational spike forengaging the surface of the skull.

DETAILED DESCRIPTION OF THE DRAWINGS

In the following detailed description, reference is made to theaccompanying drawings which form a part hereof, and in which is shown byway of illustration specific embodiments in which the invention may bepracticed. These embodiments are described in sufficient detail toenable those skilled in the art to practice the invention, and it is tobe understood that the embodiments may be combined, or that otherembodiments may be utilized and that structural, logical and electricalchanges may be made without departing from the scope of the presentinvention. The following detailed description is, therefore, not to betaken in a limiting sense, and the scope of the present invention isdefined by the appended claims and their equivalents.

In this document, the terms “a” or “an” are used, as is common in patentdocuments, to include one or more than one. Furthermore, allpublications, patents, and patent documents referred to in this documentare incorporated by reference herein in their entirety, as thoughindividually incorporated by reference. In the event of inconsistentusages between this documents and those documents so incorporated byreference, the usage in the incorporated reference(s) should beconsidered supplementary to that of this document; for irreconcilableinconsistencies, the usage in this document controls.

In this document, the term “assembly” is not intended to be limited to astructure that is assembled from multiple components, but also includesunitary or integrally-formed structures or the like.

Example 1

FIG. 1A is a schematic diagram illustrating generally, by way ofexample, but not by way of limitation, one example of an imagablefiducial marker 100 that includes a built-in divot 102. In this example,the divot 102 includes a female receptacle, such as the illustratedconical depression. However, as used herein, a divot also refers to anyother male or female receptacle, or the like. The divot 102 is capableof receiving a correspondingly sized and shaped mating tip of apositioning wand or like instrument. Such a wand or instrument is usefulfor registering the actual physical location of the patient's skull topreoperative or other images of the subject's brain. Such images aretypically stored in a memory of an image-guided surgical (IGS) computerworkstation.

In the example illustrated in FIG. 1A, the fiducial marker 100 includesan imagable substantially spherical fiducial locator 104. The fiducial104 is locatable using one or more imaging system modalities. In thisexample, a shaft 106 extends orthogonally outward from a circumferentialportion of the spherical fiducial 104. The shaft 106 includes anexternally threaded portion 108. The externally threaded portion 108 issized and shaped for being received within a correspondingly sized andshaped mating internally threaded receptacle 110 of anexternally-threaded self-tapping base 112. In this example, the base 112is capable of being mounted in a skull 114, such as either flush to (oreven recessed from) an outer surface 116 of the skull 114. One exampleof a suitable base 112 is described in commonly-assigned Mazzocchi etal. U.S. patent application Ser. No. 10/206,884 entitled FIDUCIAL MARKERDEVICES, TOOLS, AND METHODS, which was filed on Jul. 24, 2002, and whichis incorporated herein by reference in its entirety, including itsdisclosure relating to a flush or recessed mounted base and otherfiducial marker devices, tools and methods. However, in alternativeexamples, the base 112 need not be configured for mounting flush to orrecessed from the outer surface 116 of the skull 114. In this example,the shaft 106 includes a pointed tip 115. This permits the shaft 106 tomore easily penetrate a sterile drape that, in certain circumstances,may be placed over the patient's skull 114. Moreover, in this example,the receptacle 110 of the base 112 is shaped to accommodate the pointedtip 115. However, in an alternative example, the tip 115 need not bepointed.

In one example, the imaging spherical fiducial locator 104 houses agenerally spherical (e.g., except for the conic cutaway of the divot102) sealed interior cavity 118. In one example, the cavity 118 isfilled with an imagable fluid that is visible on one or more imagingmodalities (e.g., MR, CT, etc.). In this example, the apex of the conicdivot 102 is located at a center of mass of the imaging sphericalfiducial locator 104. This allows the tip of a positioning wand(recognizable by a camera in an optical position locating system that iscoupled to the image-guided surgical workstation) to be inserted intothe divot 102. This results in the wand tip being located at the centerof mass of the imaging spherical fiducial locator 104. This is usefulfor assisting in registering the physical location of the patient to thepreoperative images stored in the image-guided surgical workstation.

Unlike fiducial marker assemblies that require the user to attach animaging fiducial while obtaining the preoperative images of thepatient's brain, and to then replace that imaging fiducial with aseparate divot during patient registration in the operating room, thefiducial marker 100 illustrated in FIG. 1A does not require any suchexchange of the imaging fiducial for a separate divot. Instead, thedivot is integrated into the imaging fiducial itself, as illustrated inFIG. 1A. This reduces the complexity of the image-guided surgicalprocedure and, therefore, reduces its cost.

In one example (but not by way of limitation), the base 112 isconstructed of stainless steel. The shaft 106 and the imaging sphericalfiducial locator 104 are constructed of molded plastic polymer. In thisexample, the imaging spherical fiducial locator 104 includes an opencavity 118 for receiving the imaging fluid, and for then receiving aninsertable plastic conical divot 102 that adhesively or otherwise sealsthe cavity 118 to retain the imaging fluid therein. The imaging fluid inthe cavity 118 is visible and provides good contrast on images producedby at least one imaging modality. In one example, the imaging fluid ismultimodal (i.e., locatable by more than one imaging modality), such asby using a mixture of different imaging fluids that are locatable ondifferent imaging modalities. In an alternative example, the plasticforming the imaging spherical fiducial locator 104 includes a substancethat is viewable on a first imaging modality, while the imaging fluidwithin the cavity 118 is viewable on a different second imagingmodality.

In one such illustrative example, the plastic imaging fiducial locator104 is doped with a substance having a high atomic number (Z), such asbarium, titanium, iodine, silver, gold, platinum, iodine, stainlesssteel, titanium dioxide, etc. that provide good contrast on a CT orother radiographic imaging system. In this illustrative example, thefluid within the cavity 118 includes gadopentatate dimeglumine,gadoteridol, ferric chloride, copper sulfate, or any other suitable MRIcontrast agent, such as described in chapter 14 of Magnetic ResonanceImaging, 2^(nd) ed., edited by Stark and Bradley, 1992, which isincorporated herein by reference.

In an alternative multimodal example, the cavity 118 is omitted.Instead, the spherical fiducial locator 104 is constructed of asubstantially solid plastic or other material that is hygroscopic, thatis, capable of receiving and retaining a fluid, such as an imaging fluidthat is viewable on an imaging system (e.g., an MRI imaging system orthe like). In a further example, the plastic forming the sphericalfiducial locator 104 is doped or otherwise includes a substance that isviewable on a different imaging system, such as, for example, a CT orother radiographic imaging system. Illustrative examples of solidplastics that can be made hygroscopic include, among other things, nylonand polyurethane. Using a hygroscopic material avoids the complexity andcost associated with manufacturing a sealed cavity 118 for retaining animaging fluid. Moreover, by adapting the solid hygroscopic plastic forimaging using a first modality, and by using the imaging fluid forimaging using a second modality, each of the solid and the fluid can beseparately tailored toward providing better contrast for its particularimaging modality.

In another alternative example in which the cavity 118 is omitted, thefiducial locator 104 includes a rigid solid (e.g., substantiallyspherical, but for the conic divot) interior. This solid material isdoped with a substance that provides good contrast using a first imagingmodality (e.g., CT). A hygroscopic outer coating is formed thereupon.The coating permits soaking up a fluid that provides a good contrastusing a second imaging modality (e.g., MRI).

In a further example of the fiducial marker 100 illustrated in FIG. 1A,the outer surface of the imaging spherical fiducial locator 104 isreflective of light or other electromagnetic energy. Consequently, it isalso locatable by the operating room camera in an optical positioningsystem that is coupled to the image-guided workstation (e.g., duringpatient registration). In one such example, the outer surface of theimaging spherical fiducial locator 104 includes light-reflectivemicro-spheres (e.g., embedded in an adhesive covering the imagingspherical fiducial 104). In another such example, the outer surface ofthe imaging spherical fiducial 104 is covered with an adhesive-backedlight-reflective tape, such as SCOTCHLITE® 9810 Reflective MaterialMultipurpose Tape sold by Minnesota Mining and Manufacturing Co.(“3M®”), of Saint Paul, Minn.

FIG. 2A is a schematic diagram illustrating generally, by way ofexample, but not by way of limitation, an alternative example of afiducial marker 200 that includes a generally cylindrical imagingfiducial locator 202 and a conical or other divot 102. In one example,the generally cylindrical imaging fiducial locator 202 includes a sealedcavity 204 for receiving and retaining an imagable fluid, as discussedabove. In another example, the sealed cavity 204 is omitted, asdiscussed above. In one such example, the generally cylindrical imagingfiducial locator 202 is instead constructed of a substantially solidhygroscopic plastic that carries an imagable fluid (as discussed above),such as for providing multimodal contrast across different imagingmodalities. In a further example, the generally cylindrical outersurface of the imaging fiducial locator 202 is reflective, as discussedabove, such that the imaging fiducial locator 202 is also visible to acamera of an optical position locating system that is coupled to animage-guided surgical workstation (e.g., during patient registrationand/or a subsequent image-guided surgical procedure). In one suchexample, the imaging fiducial locator 202 is covered withadhesive-backed reflective tape taken from a rectangular strip of suchtape that is wound into a roll. In this example, the generallycylindrical shape of the outer surface of the imaging fiducial locator202 is much easier to wrap using a wound rectangular strip of theadhesive reflective tape than a spherical surface, such as isillustrated in FIG. 1A, and therefore costs less to manufacture. In thisdocument, the term “generally cylindrical” is not limited to a perfectlycylindrical surface, but instead is understood to include any faceted orother column or like structure (e.g., an octogonal cylinder a hexagonalcylinder, etc.) that includes a lateral peripheral surface that easilyaccommodates receiving a wound rectangular or similar strip of tape (asopposed to a spherical, elliptical, or conical surface, to which is moredifficult to evenly apply a wound rectangular strip of tape taken from aroll). Examples of such generally “cylindrical” columnar structureshaving faceted lateral peripheral surfaces are illustrated in FIG. 3C.

In an alternate example to the illustrations of FIGS. 1A and 2A, thedivot 102 is omitted from the fiducial marker 100 or 200. However, theresulting fiducial marker is still configured to be locatable by aremote positioning system as well as imagable using one or more imagingmodalities. In one such example, the outer surface 104 or 202 is stillconfigured to be light reflective, such as discussed above. In one suchexample, the fiducial markers 100 and 200 still advantageously arelocatable using one or more imaging modalities (e.g., MR, CT, or otherimaging system providing 3D or other internal images within a subject)as well as also being locatable external to the subject, such as byusing a remote camera or like component of an optical or otherpositioning system, e.g., that is coupled to an image-guidedworkstation. In one example, this permits automatic registration of theactual location of the subject in the operating room (e.g., using thecameras to locate the light reflective fiducial markers 100 or 200) topreoperative images of the patient on which the same imagable fiducialmarkers 100 and 200 appear. This eliminates any need to register thepatient by inserting an optically-locatable positioning wand tip into adivot of each fiducial marker (and also eliminates any need for areference divot or other absolute position reference), because thefiducial markers themselves are optically locatable and registerable toknown locations on the preoperative images. Therefore, in this example,the divots 102 are not needed and can be omitted, as illustrated by thedivotless spherical imagable reflective fiducial marker 120 in FIG. 1Band the divotless cylindrical imagable reflective fiducial marker 206 inFIG. 2B. Although FIG. 2B illustrates an example including a cavity 204for carrying a liquid contrast agent, in an alternative example, thecavity 204 is omitted, and the fiducial marker 206 includes a solidstructure that is doped or otherwise configured (e.g., hygroscopic) forproviding good imaging contrast using one (e.g., CT) or more imagingmodalities.

In yet another example, the fiducial markers 100 and 200 respectivelyillustrated in FIGS. 1A and 2A include the illustrated divots 102 andare locatable by a remote positioning system (such as by includinglight-reflective outer surfaces and/or embedded coils that performmagnetic field sensing in a magnetic field based positioning system).However, in this example, the fiducial markers 100 and 200 need not beconfigured for providing contrast on the one or more imaging modalities.In such an example, the preoperative images are taken with imagablefiducial markers placed within respective bases 112. Such imagablefiducial markers are then replaced (within their respective bases 112)by nonimagable fiducial markers that are locatable by a remotepositioning system, such as by including both a divot and alight-reflective surface. The light reflective surface permits automaticlocation by the remote positioning system. However, if the reflectivesurface is dirty or otherwise unrecognizable by the remote positioningsystem, a wand or other locating instrument can be placed within thedivot to perform the remote locating of the fiducial marker.

Moreover, although FIGS. 1A and 2A illustrate examples in which a shaft106 is received within a base 112 that is mounted flush to (or recessedfrom) the outer surface 116 of the skull 114, this is not required. Inone alternate example, the shaft 106 is manufactured as a stainlesssteel or other suitable material that is capable of acting as aself-tapping bone screw. In such an example, the threaded portion 108 ofthe shaft 106 is threaded directly into the skull 114 without using anybase 112. In another alternate example, the base 112 includes a shaft orflange portion that rises above the outer surface 116 of the skull 114.In certain examples, the fiducial markers 100 and 200 may use a threadedor other shaft 106 for coupling to the base 112, or alternatively mayuse a snap-fit clip or a like attachment device for coupling to the base112.

FIG. 3A is a schematic diagram illustrating generally, by way ofexample, but not by way of limitation, one example of a positioning wand300, such as for use with a remotely-located camera or other like deviceof an optical positioning system configured for being coupled to animage-guided surgical workstation in an operating room. In this example,the wand 300 includes a tip 302 that is sized and shaped to permit beingreceived in a divot 102 of a skull-mounted fiducial marker (such asfiducial markers 100 and 200). The wand 300 includes a plurality ofcylindrically-shaped fiducial locators 304 that are locatable by thecamera or other like device of the optical positioning system. Thefiducial locators 304 (which typically need not include divots) on thewand 300 are positioned in a known spatial relationship to each otherand to the tip 302 of the wand 300. By recognizing the locations of thefiducial locators 304, the optical positioning system is capable ofcomputing the location of the wand tip 302, which is in a known spatialrelationship with the configuration of fiducial locators 304. Thispermits the wand 300 to be used in conjunction with the opticalpositioning system to register the patient and to further plan and/orperform the surgical procedure using the image-guided surgicalworkstation. The fiducial locators 304 are covered with adhesive-backedreflective tape, as discussed above. The cylindrical (or facetedcylindrical) shape of the fiducial locators 304 permits easier wrappingby the reflective tape than the spherical fiducials, as discussed above.This reduces the cost of manufacturing the fiducial locators 304 and, inturn, reduces the cost of manufacturing the positioning wand 300.

FIG. 3B is a schematic diagram, similar in certain respects to FIG. 3A,but illustrating a wand 306 that includes locators 308A-C havingswiveling or fixed cylindrical locators 308A-C having respective slanted(e.g., flat, parabolic, or other) top surfaces 310A-C (e.g.,non-orthogonal with respect to a longitudinal center axis 311 of thelocator 308) that reflect light or other electromagnetic energy forbeing located by a remote detector. In an example in which the locators308A-C swivel, each such locator 308 includes a shaft inserted into ahole or other receptacle in the wand 306. This permits the locator 308to rotate with respect to its mounting location on the wand 306. Eitherthe wand 306 itself or the individual locators 308A-C are oriented bythe user to aim the reflective surfaces 310A-C toward a camera or otherdetector of an optical positioning system. In one further example, thecircumferential surfaces of the cylindrical locators 308A-C are alsolight-reflective, however, this is not required. In one suchcost-effective example, the reflective tape disks are adhered to theflat slanted top surfaces 310A-C and the circumferential lateralsurfaces of the cylindrical locators 308A-C are not reflective.

FIG. 3C is a perspective view schematic diagram illustrating generally,by way of example, but not by way of limitation, certain generally“cylindrical” columnar structures 312, 314, and 316 having facetedlateral peripheral surfaces. Such surfaces are conducive to receiving arectangular or like strip of adhesive reflective tape. Such structures,therefore, are particularly well-suited for implementing locators thatare remotely locatable by an optical positioning system. Such remotelydetectable locators are suitable for use in the fiducial markersillustrated in FIGS. 2A and 2B, as well as for use in the remotelydetectable locators of the positioning wands illustrated in FIGS. 3A and3B. Such remotely detectable locators are also useful for being affixedin a known relationship to the patient, such as to the operating tableor to a skull-immobilizing headframe. This provides a remotelydetectable absolute positional reference to an optical positioningsystem. Such remotely detectable locators are also useful for beingaffixed to a biopsy needle, shunt catheter, or other instrument beingintroduced through a trajectory guide device or otherwise used in animage-guided surgical procedure.

FIG. 3D is a schematic diagram illustrating generally, by way ofexample, but not by way of limitation, an alternative example of apositioning wand 318. In this example, which flat disk-shaped pieces ofreflective tape are attached to the wand 318 in a known configuration,such as at the distal ends of radial arms extending therefrom.

Example 2

FIG. 4 is a schematic diagram illustrating generally, by way of example,but not by way of limitation, an image guided surgical (IGS) computerworkstation 400, which is capable of displaying previously acquired andloaded preoperative images of a patient's skull. On these preoperativeimages appear viewable images of imagable fiducial markers that werescrewed into the patient's skull before the preoperative imaging (e.g.,using MRI, CT, etc.). In the example illustrated in FIG. 4, the imagablefiducial locators have been unscrewed from respective bases 402 screwedinto the patient's skull. The imagable fiducial locators have beenreplaced by patient registration divot assemblies 404 that have beenscrewed into (or otherwise coupled to) respective bases 402 in thepatient's skull 114. In this example, the registration divot assemblies404 are configured to receive a shaft tip 406 of a positioning wand 408that is locatable by one or more remote cameras 410A-B (or other sensingdevices) of an optical position detection system 412 connected to theIGS workstation 400. In one example, the positioning wand 408 includesspherical reflective fiducial locators 414. The fiducial locators 414are arranged in a known spatial relationship to each other (however, itmay alternatively use other reflective locators such as discussedelsewhere in this document). The optical positioning system 412 includesan infrared light (or other energy source) 416 that provides light thatis reflected from the reflective fiducial locators 414. This permits thereflective fiducial locators 414 on the positioning wand 408 to belocated and recognized by the cameras 410A-B. In some circumstances,however, the field of view (or “sweet spot” of the field of view)provided by cameras 410A-B is limited. This sometimes makes it difficultfor the optical positioning system 412 to recognize the positioning wand408. Moreover, the recessed receptacle in the divot assembly 404typically limits the range within which the probe 408 can be manipulated(e.g., to bring it within the field of view) while retaining the wandtip 406 within the recessed receptacle.

FIG. 5 is a schematic diagram illustrating generally, by way of example,but not by way of limitation, a unitary divot assembly 500 that includesmultiple divots 502. In this example, the unitary divot assembly 500 isconfigured such that it can be threaded into or otherwise coupled to abase 504 that is secured to the patient's anatomy (wherein the base 504is also configured for alternatively receiving an imagable fiduciallocator, e.g., during preoperative imaging). FIG. 5 illustrates multipleconical receptacle divots 502 having commonly located apexes. Thesecommonly located apexes are designed to coincide with the center of theimage produced by the imagable fiducial locator for which the divotassembly 500 has been substituted during patient registration. In theillustrated example, the divots include a top conical divot 502A andfour side conical divots 502B-F. The four side conical divots 502B-F aredistributed around the cylindrical lateral peripheral circumference ofthe upper portion of the divot assembly 500. The wand tip 406 may beinserted into any one of the divots 502. This permits a greater range ofmotion of the positioning wand 408. As a result, it is easier to bringthe reflective fiducials 414 on the positioning wand 408 into the fieldof view of the cameras 410A-B of the optical positioning system 412.

FIG. 6A is a schematic diagram illustrating generally, by way ofexample, but not by way of limitation, a divot assembly 600 thatincludes a swiveling tilted head 602 carrying a conical or other divot604 or the like. In this example, the head 602 is tilted with respect toa cylindrical coupling 606 extending outwardly therefrom. The coupling606 includes a hollow interior or other (female or male) connector thatsnap-fits onto and rotatably rides upon a mating (male or female)connector 608 that is located at a proximal end of a shaft 610 portionof the divot assembly 600. The swiveling apex 612 of the divot 604 isdesigned to coincide with the center of mass of the imagable fiduciallocator for which the divot assembly 600 has been substituted duringpatient registration. The swiveling tilted head 602 permits a wide rangeof motion of the positioning wand 408 when the wand tip 406 is insertedinto the divot 604. As a result of such rotational articulation, it iseasier to bring the reflective fiducial locators 414 on the positioningwand 408 into the limited field of view of the cameras 410A-B of theoptical positioning system 412.

FIG. 7A is a schematic diagram illustrating generally, by way ofexample, but not by way of limitation, a divot assembly 700 thatincludes a swiveling and pivotable head 702 carrying a conical or otherdivot 704. In this example, the head 702 is carried by a shackle-likeU-shaped bracket 704 that rotatably rides upon a snap-fit or othercapturing post 706 that extends upward from a shaft portion 708 of thedivot assembly 700. This allows swiveling of the bracket 704 (and thehead 702 carried by the bracket 702) with respect to the shaft 708. Inthis example, the head 702 is suspended between upward-projecting risersof the bracket 704 by axels 710A-B extending outward from opposing sidesof the head 702 and received within corresponding receptacles in therisers of the bracket 704. This permits pivoting/tilting articulation ofthe head 702 with respect to the swiveling bracket 704. Therefore, thisexample provides a swiveling and adjustably tiltable divot 704 that isdesigned such that its apex 712 coincides with the center of mass of theimagable fiducial locator for which the divot assembly 700 has beensubstituted during patient registration. Among other things, theswiveling tiltable head 702 advantageously permits a greater range ofmotion of the positioning wand 408 when the wand tip 406 is insertedinto the divot 704. As a result, it is easier to bring the reflectivefiducials 414 on the positioning wand 408 into the limited field of viewof the cameras 410A-B of the optical positioning system 412.

FIGS. 6B and 7B are schematic diagrams that are similar in certainrespects to FIGS. 6A and 7A. However, the locator assemblies 614 and 714illustrated by respective FIGS. 6B and 7B omit the respective divots 604and 704. Instead, the locator assemblies 614 and 714 provide aimableelectromagnetic energy (e.g., light) reflective surfaces 616 and 716,respectively. The reflective surfaces 616 and 716 are aimed at thecamera of an optical positioning system 412 to allow automatic detectionof the locator assemblies 614 and 714 without requiring the use of apositioning wand 408.

The reflective surfaces 616 and 716 are configured so that, when aimedproperly, they produce a reflected image that can be correlated to apreviously acquired patient image on which an image of an imagablefiducial marker appears. In one such example, reflective surface 616corresponds to the center of mass of a similarly sized spherical locatoron an imagable fiducial marker assembly for which locator assembly 614is substituted during patient registration. In another such example,reflective surface 716 includes a circular disk-shaped piece ofreflective tape affixed to a surface 718 such that this reflective diskpivots about the axis provided by axels 710A-B. In this manner, thereflected disk shape corresponds to the center of mass of a similarlysized spherical locator on an imagable fiducial marker assembly forwhich locator assembly 714 is substituted during patient registration.

Example 3

As discussed above, screwing multiple fiducial markers into differentlocations in the patient's skull 114 results in trauma and/or risk ofinfection at each one of such multiple different locations. FIG. 8 is aschematic diagram illustrating conceptually, by way of example, but notby way of limitation, a fiducial marker carrier 800 that is attachableto (and also detachable from) a single location on the patient's skull114, thereby reducing trauma and risk of infection to the patient. Inthis example, the fiducial marker carrier 800 is configured for carryingmultiple different imagable fiducial locators 802 such that they arepositioned at different locations about the patient's skull 114. Asdiscussed below, the carrier 800 uses a keyed mounting arrangement, suchthat the carrier 800 can be attached to the patient's skull 114, thendetached from the patient's skull 114, and later reattached to thepatient's skull 114 in the same orientation in which it was initiallyattached to the patient's skull 114.

In the example illustrated in FIG. 8, the carrier 800 includes a keyedframe 804 that is attached to a keyed post 806 for mounting. The keyedpost 806 is, in turn, attached to a single flush-mounted orrecessed-mounted or other keyed base 808, which was previously screwedinto the patient's skull 114. This keyed arrangement of the frame 804,the post 806, and the base 808 permits attachment, detachment, andreattachment in the same orientation as the original attachment, asdiscussed above. In an alternative example, the post 806 is integrallyformed as part of the frame 804, rather than being keyed for attachmentthereto.

In one example, such illustrated in FIG. 8, the imagable locators 802are placed about the subject's head such that they surround thepatient's skull. Although such a surrounding arrangement is notrequired, it is believed to improve the accuracy of using the images ofthe locators 802 (e.g., in conjunction with the IGS workstation) forplanning and/or performing an image-guided surgical procedure, ascompared to an arrangements in which locators are disposed more closelytogether (e.g., on the same side of the subject's head).

FIG. 9 is an exploded view schematic diagram illustrating generally, byway of example, but not by way of limitation, one example of the carrier800, including the frame 804, the post 806, and the base 808. In thisexample, the base 808 includes self-tapping external threads 902, and iscapable of being mounted flush with (or even recessed within) thepatient's skull 114. The base 808 includes an internally-threadedreceptacle 904 that is sized and otherwise configured such that it iscapable of receiving a screw. The base 808 also includes a female ormale keying feature for receiving a mating keying feature of the post806 to fixedly define the orientation of the post 806 with respect tothe base 808. In one example, the keying feature includes a key slot 906extending radially outward from the receptacle 904 along a proximalsurface of the base 808.

The post 806 includes a proximal end 908 and a distal end 910. The post806 includes a center lumen 912 in which an attachment screw 914 isreceived and seated. The screw 914 attaches the post 806 to the base808. The distal end 910 of the post 806 includes a male or female keyingfeature (such as a key protrusion 916 extending radially outward fromthe center lumen 912 along the distal end 910 of the post 806) thatmates with the keying feature (e.g., key slot 906) of the base 808. Suchmating during the attachment fixedly defines the orientation of the post806 with respect to the base 808.

In this example, the center lumen 912 includes a keyed seatingreceptacle 918 (or an analogous male keyed feature) for receiving amating keyed feature of the frame 804. In the illustrated example ofFIG. 9, the keyed seating receptacle 918 includes an increased diameterof the center lumen 912 (with respect to more distal portions of thecenter lumen 912) to provide the seating, and a radially-outwardlyextending slot 920 to provide the keying.

In the example illustrated in FIG. 9, the frame 804 includes legs 922A-D(or a fewer or greater number of legs 922), such as extending radiallyoutwardly from a hub 924 and downwardly toward the middle portion of thepatient's skull. Each of the legs 922 includes, such as at itsrespective distal end, a threaded receptacle 924A-D (or a snap-fittingor any other coupling) for receiving at least one of an imagablefiducial marker assembly 926, a divot assembly 928, a locator assembly930 (e.g., reflector, LED, microcoil, etc.) that is remotely detectableby a positioning system in an operating room, or a combination 932 oftwo or more of the above. In an alternative embodiment (for examplewhere a combination 932 includes an imagable locator and at least one ofan operating room position locator and a divot), instantiations of sucha combination 932 may be permanently affixed to corresponding locationson the legs 922 of the frame 804.

In the example illustrated in FIG. 9, the hub 924 portion of the frame804 also includes a downwardly protruding key 934 (or analogous femalereceptacle) that mates to the keyed seating receptacle 918, of the post806, into which the key 934 is received. This fixedly defines theorientation of the frame 904 with respect to the post 806. A screw 936is inserted through the hub 924, the key 934, and into an engaginginterior threaded portion of the center lumen 912. This securelyattaches the frame 904 to the post 806 in the fixedly definedorientation. The example illustrated in FIG. 9 also includes at leastone optional instrument mount 938. In one example, a reference divot(e.g., providing a position reference) is attached to the instrumentmount 938.

Although FIGS. 8 and 9 illustrate examples in which a fiducial markercarrier 800 is mounted using a single base 808, in other examples, thecarrier may be mounted using two or more bases 808 at the same locationon the patient's skull (that is, at adjacent locations within the samescalp incision, or like limited trauma/infection risk zone; the incisionneed only be large enough to accommodate the two or more bases 808).Using two or more side-by-side bases 808 to attach the post 806 avoidspotential rotational misalignment of a single base 808 coming slightlyunscrewed from its original position.

Alternatively, if a single base 808 is used, such rotationalmisalignment can be avoided by including one or more antirotation spikes1000 on the bottom of the distal end 910 of the post 806, such asillustrated generally in FIG. 10. In the example illustrated in FIG. 10,the distal end 910 of the post 806 is keyed both to the base 808 and,using the antirotation spike(s) 1000, to indentation(s) made in thesurface 116 of the skull 114. However, in an alternative example, thepost 806 and the base 808 need not be keyed to each other. Instead, insuch an example, the post 806 is keyed only to indentation(s) made bythe antirotation spike(s) 1000 in the surface 116 of the skull 114.

In further examples, the various above-described locators (e.g., on thesubject's skull, or on a wand, as illustrated in FIG. 3) alternativelyor additionally include an electromagnetic (EM) coil that permitsdetermination of the position of the locator using an EM coil detectingpositioning system coupled to an IGS workstation rather than the opticalpositioning system 412 discussed above.

It is to be understood that the above description is intended to beillustrative, and not restrictive. For example, the above-describedembodiments may be used in combination with each other. Many otherembodiments will be apparent to those of skill in the art upon reviewingthe above description. The scope of the invention should, therefore, bedetermined with reference to the appended claims, along with the fullscope of equivalents to which such claims are entitled. In the appendedclaims, the terms “including” and “in which” are used as theplain-English equivalents of the respective terms “comprising” and“wherein.” Moreover, in the following claims, the terms “first,”“second,” and “third,” etc. are used merely as labels, and are notintended to impose numerical requirements on their objects.

1. An apparatus comprising: a fiducial marker including: a substantiallyspherical fiducial locator locatable in an image using one or moreimaging system modalities; and a shaft extending orthogonally outwardfrom a curved portion of the spherical fiducial locator, wherein theshaft has an externally threaded portion at an end; and anexternally-threaded self-tapping base having an internally threadedreceptacle correspondingly sized and shaped to mate with the externallythreaded portion of the shaft; wherein the externally-threadedself-tapping base is capable of being mounted entirely in a skull eitherflush to or recessed from an outer surface of the skull; wherein theshaft includes a pointed tip; wherein the spherical fiducial locatorincludes a plurality of conical divots each including an apex that isintegrally located within the fiducial locator, such that a center ofthe image of the fiducial locator substantially coincides with the apexof the respective plurality of divots; wherein the spherical fiduciallocator defines a generally spherical sealed interior cavity, except forthe plurality of conical divots; wherein the spherical fiducial locatoris operable for patient registration to the images because the sphericalfiducial locator is locatable in the images of a patient and thespherical fiducial locator including the plurality of conical divots arelocatable relative to the patient when the patient is in an operatingroom.
 2. The apparatus of claim 1, wherein the cavity is filled with animagable fluid that is visible in one or more imaging modalities.
 3. Theapparatus of claim 2, wherein the spherical fiducial locator is formedof a substance that is viewable on a first imaging modality and theimagable fluid is viewable on a different second imaging modality. 4.The apparatus of claim 1, further comprising: a positioning wandincluding a tip; wherein an apex of each of the plurality of conicaldivots are located at a center of mass of the spherical fiduciallocator; wherein the wand tip is operable to be located at the center ofmass of the spherical fiducial locator.
 5. The apparatus of claim 4,wherein the externally-threaded self-tapping base extends from aninsertion end to a receptacle end that defines an opening to theinternally threaded receptacle and has an external maximum dimensionthat is defined by an external thread, wherein the external maximumdimension is defined by the externally-threaded self-tapping base at thereceptacle end.
 6. The apparatus of claim 5, further comprising: asecond fiducial marker including an electromagnetic coil and operable tobe positioned in the externally-threaded self-tapping base after thefiducial marker including the substantially spherical fiducial locatorand shaft has been removed from the externally-threaded self-tappingbase; wherein the second fiducial marker is automatically locatable by aremote positioning system including a system electromagnetic coil. 7.The apparatus of claim 5, wherein the fiducial marker is formed of afirst material and the externally-threaded self-tapping base is formedof a different second material.
 8. An apparatus comprising: a fiducialmarker including: a fiducial locator locatable in images using one ormore imaging system modalities; a shaft extending orthogonally outwardfrom a portion of the fiducial locator, wherein the shaft has a pointedtip and an externally threaded portion at the pointed tip; a reflectiveouter lateral peripheral surface that reflects electromagnetic energy;and a plurality of conical divots extending into the fiducial locatorfrom the outer lateral peripheral surface; and an externally-threadedself-tapping base having an internally threaded receptaclecorrespondingly sized and shaped to mate with the externally threadedportion of the shaft; wherein the plurality of conical divots areseparately formed in the lateral peripheral surface and configured sothat a positioning wand tip is operable to be placed in any of theplurality of conical divots to permit a greater range of motion of thepositioning wand relative to the fiducial marker.
 9. The apparatus ofclaim 8, wherein the fiducial locator is generally cylindrical exceptfor the plurality of conical divots; wherein the fiducial locatorincludes a sealed cavity for receiving and retaining an imagable fluid,wherein the fiducial locator is both operable to be identified in theimages and operable to be registered to an identified fiducial locatorin the images during patient registration in an operating room with atleast one of the plurality of conical divots.
 10. The apparatus of claim9, wherein the fiducial locator is formed of a first material thatincludes a substance that is viewable on a first imaging modality andthe imaging fluid within the cavity is viewable on a different secondimaging modality.
 11. The apparatus of claim 8, wherein the fiduciallocator is faceted to include at least one facet, and the facet includesthe lateral peripheral surface that accommodates receiving a woundrectangular strip of tape.
 12. An apparatus comprising: a fiducialmarker including: a fiducial locator locatable in images using one ormore imaging system modalities; a shaft extending orthogonally outwardfrom a portion of the fiducial locator, wherein the shaft has a pointedtip and an externally threaded portion at the pointed tip; a reflectiveouter lateral peripheral surface that reflects electromagnetic energy;and a plurality of conical divots, wherein at least one of the pluralityof conical divots extends into the fiducial locator from the outerlateral peripheral surface; and an externally-threaded self-tapping basehaving an internally threaded receptacle correspondingly sized andshaped to mate with the externally threaded portion of the shaft;wherein each of the plurality of conical divots includes an apex that isintegrally located within the fiducial locator, such that a center ofthe image of the fiducial locator substantially coincides with the apexof the respective plurality of divots.
 13. An apparatus comprising: afiducial marker constructed of at least a first material including: afiducial locator locatable in an image using one or more imaging systemmodalities and defines an internal cavity; a shaft extendingorthogonally outward from an external portion of the fiducial locator,wherein the shaft has an externally threaded portion at an end; aplurality of conical divots all separately formed in a surface of thefiducial locator; and an imaging fluid in the internal cavity that isvisible and provides good contrast on images produced by at least oneimaging modality; and an externally-threaded having an internallythreaded receptacle correspondingly sized and shaped to mate with theexternally threaded portion of the shaft; wherein theexternally-threaded self tapping base is capable of being mountedentirely in a skull either flush to or recessed from an outer surface ofthe skull; wherein the shaft includes a pointed tip; wherein each of theplurality of conical divots of the insertable member is sized and shapedto receive a tip of a positioning wand for patient registration to animage space of the image that has imaged the fiducial locator.
 14. Theapparatus of claim 13, wherein the fiducial locator is formed of a firstmaterial including a substance that is viewable on a first imagingmodality and the imaging fluid within the cavity is viewable on adifferent second imaging modality.
 15. The apparatus of claim 14,wherein an apex of each of the plurality of conical divots is integrallylocated within the fiducial locator, wherein the apex of each of theplurality of conical divots is located at a center of mass of thefiducial locator such that an image of the fiducial locatorsubstantially coincides with the apex of each of the plurality ofconical divots.
 16. The apparatus of claim 15, further comprising: apositioning wand including a tip; wherein the tip is sized and shaped tobe received in each of the plurality of conical divot divots to belocated at the center of mass of the fiducial locator.
 17. The apparatusof claim 16, wherein the externally-threaded self-tapping base extendsfrom an insertion end to a receptacle end that defines an opening to theinternally threaded receptacle and has an external maximum dimensionthat is defined by an external thread, wherein the external maximumdimension is defined by the externally-threaded self-tapping base at thereceptacle end.
 18. The apparatus of claim 13, further comprising: asecond fiducial marker including a first electromagnetic coil andoperable to be positioned in the externally-threaded self-tapping baseafter the fiducial marker has been removed from the base, wherein thesecond fiducial marker is locatable by a remote positioning systemincluding a second electromagnetic coil; wherein the externally-threadedself-tapping base extends from an insertion end to a receptacle end thatdefines an opening to the internally threaded receptacle and has anexternal maximum dimension that is defined by an external thread,wherein the external maximum dimension is defined by theexternally-threaded self-tapping base at the receptacle end.